From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 713063C140C; Tue, 17 Mar 2026 13:06:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773752772; cv=none; b=YbDmV10pa8XmCWHfHKJYjY9YWSxoe/Foyplw93VOAlN8Ox1xRYhH+jmiYxYURAqZPse/IrnAjoIGDMAlYdc9+1fn9CmWhAd4Nu++CBEnjGcGgGK91GXLtHS1r6rbwcANRH7eR652UZxbHqci+AWrhJS8KoHFVVloOtsYYhf8Li0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773752772; c=relaxed/simple; bh=Psbirt/YP7hNGPqGR4mZdh4NA6DQF0ohxeq1831l9KE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ou9RhyGrW4rGwcuotV2+LCN7uOCE0fypPZsqcw8zOm+LTD4otGRLZsI91sG/AhaM+6XbYlY1oKv1D9plzju+NqZhO7/2gF+bmLkp6cuZRnZ+YQZzV5rZW3JyoNcJYcnkQdbr2ByEipMdaXjaPIvKc1pQl46pnWeBeLMbuWDB00o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gKIPqh0w; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gKIPqh0w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB425C19425; Tue, 17 Mar 2026 13:05:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773752772; bh=Psbirt/YP7hNGPqGR4mZdh4NA6DQF0ohxeq1831l9KE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gKIPqh0wjUeANGMDdq7LVx5gZCDNbXAI3zeBGD+RFqIx1XJ6omk9ZYbGXbcPWi3No ionisDQH5w4gli0Yi0kg8zTkv1UWw+2fdHqZfC3jOylVwAPd9jz1zdJOs0sh84Bbh6 IynphC85kTHWzw33qqswiVuCuxXiDIUas+pYdgG3uLOAFrmG2IqadkNToYIzm6KmU7 A0ohkV7z3dmqJBPiGVDi+NdVWQr/mnCzvEQTyy40eANihkKBiWr3avR2L4ligsr5vG eOXx/kO5s9EFSzLM3C0H9YOWa2BqRac1wxr2HiR/AnMA0g24pwGm12G3i1xVv8/i95 PC0YTXsmgngyw== Message-ID: <049d056b-844b-4480-b90e-bf4c850fc70e@kernel.org> Date: Tue, 17 Mar 2026 14:05:53 +0100 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM) To: Gregory Price Cc: linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, kernel-team@meta.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, dan.j.williams@intel.com, longman@redhat.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com, sj@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, jannh@google.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, pfalcato@suse.de, rientjes@google.com, shakeel.butt@linux.dev, riel@surriel.com, harry.yoo@oracle.com, cl@gentwo.org, roman.gushchin@linux.dev, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, zhengqi.arch@bytedance.com, terry.bowman@amd.com References: <20260222084842.1824063-1-gourry@gourry.net> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/23/26 17:08, Gregory Price wrote: > On Mon, Feb 23, 2026 at 09:54:55AM -0500, Gregory Price wrote: >> On Mon, Feb 23, 2026 at 02:07:15PM +0100, David Hildenbrand (Arm) wrote: >>> >>> I'm concerned about adding more special-casing (similar to what we already >>> added for ZONE_DEVICE) all over the place. >>> >>> Like the whole folio_managed_() stuff in mprotect.c >>> >>> Having that said, sounds like a reasonable topic to discuss. >>> >> >> Another option would be to add the hook to vma_wants_writenotify() >> instead of the page table code - and mask MM_CP_TRY_CHANGE_WRITABLE. >> > > scratch all this - existing hooks exist for exactly this purpose: > > can_change_[pte|pmd]_writable() > > Surprised I missed this. > > I can clean this up to remove it from the page table walks. Sorry for the late reply -- sounds like we can handle this cleaner. But I am wondering: why is this even required? Is it just for "Services that intercept write faults (e.g., for promotion tracking) need PTEs to stay read-only" But that promotion tracking sounds like some orthogonal work to me. What am I missing that this is required in this patch set? (is it just for the special compressed RAM bits?) -- Cheers, David